Parts and structures of objects, in particular moving objects like vehicles of any kind, can be subject to stress caused by an impact. The stress or force of an impact can cause damage to parts and structures, either directly or indirectly, and lessening or avoiding such damage can be desirable. Examples of applications where parts and structures may be subject to impact forces include vehicles of any kind, for example, land vehicles, water going vehicles, under-water vehicles, air vehicles and space vehicles. Other examples are parts and structures in industrial applications, manufacturing applications, household applications, farming applications, and any other application where added protection against impact forces is desired. Specific examples of parts and structures that may suffer under impact forces, and that may benefit from a protector, are sprockets used in vehicles, including on bicycles, motorcycles, and ATVs. Protecting sprockets can pose a challenge. Problems may arise where an impact may lead to bending and deformation or to movement of mounting components under impact. A specific concern pertains to bicycle sprocket protection, where an impact protector is mounted to a bicycle crank arm, substantially coaxially with a sprocket or cluster of sprockets. The bicycle crank arm is designed to transfer force from the rider's legs to the sprockets and from the sprockets to the driving wheel. Impact at an impact protector for bicycle sprockets can typically bend the crank arm, which then requires replacement. Other problems may arise from the manner in which a protector is attached or mounted to protect certain parts or structures. For example, impact protector mountings are less desirable if they transmit excessive impact forces onto parts that are not designed to withstand such forces. For example, bicycle impact protectors that are mounted by merely clamping the protector to a frame using a bicycle bottom bracket as a single bolted connection may result in damage to a bottom bracket or bicycle drivetrain component under impact. Examples of such protectors are shown in U.S. Pat. No. 7,066,856. Bicycle bottom brackets thread into bicycle frames to provide a rotational mounting for bicycle crank arms. Bicycle bottom brackets are not well suited to mitigate significant impact forces. An impact on a bottom bracket can damage the bottom bracket, possibly causing an unsafe operating condition for the rider. Another concern in the design of impact protectors are movements of the impact protector in case of an impact. For example, impact protector designs that clamp between the bottom bracket and bicycle frame can rotate during impact and thereby expose components they were aimed to protect against impact forces. Yet another consideration in designing impact protectors are the means by which the protector is attached. For example, where screws are used to gouge the impact protector into the bicycle frame, dangerous frame damage from the points of the screws may result. Also, elaborate and heavy clamping mechanisms are not ideal due to the extremely large number of frame design variations and layouts. Additionally, due to the lightweight nature of bicycle frame designs and the reliance on thin walled tubing, clamp type designs such as disclosed in U.S. Pat. Nos. 5,067,930 and 7,066,856 can cause structural damage by crushing thin walled tubes during clamping. Further challenges arise for bicycle impact protector mountings when considering the need for chainguides on bicycles. Many bicycles used for downhill and aggressive type riding include devices known as chain guides or chain retention systems to prevent derailment of a chain on a front sprocket or sprockets of a bicycle. Typically these devices incorporate an outer and inner impact protector mounted to the bicycle crank arm. Some designs use an outer impact protector that is mounted to a bicycle crank arm, in conjunction with an inner impact protector that is an integrated part of an inner chain guide plate. These designs frequently pose problems when the inner protector deforms due to impact and causes binding in, or damage to, the bicycle drivetrain.
There is a need for impact protector mountings that can minimize damage to mounting components, bicycle crank arms, bottom brackets, frames, or other parts. A need also exists for mountings that can maintain the location of the protector in relation to parts that are to be protected. A need further exists for mountings that are sufficiently light in weight. Furthermore, a need exists for impact protector mountings that integrate with bicycle chainguides while minimizing damage to bicycle crank arms, bottom brackets, frames, or other parts. Finally, a need exists for protector mountings that are more cost effective. The present invention provides impact protector mountings that satisfy one or more of these needs.